Field effect transistors are semiconductor devices that are commonly found in a wide variety of integrated circuits. When a voltage is applied to a gate of the transistor that is greater than a threshold voltage, the transistor is turned on, and current may flow through the transistor. When the voltage at the gate is less than the threshold voltage, the transistor is off, and current does not flow through the transistor. The gate permits electrons to flow though or blocks their passage by creating or eliminating a channel between a source and a drain. Electrons flow from the source towards the drain through the channel.
Field emission transistors are similar semiconductor devices. However, instead of a gate or channel in between the source and drain, there is a void (e.g., vacuum, ambient, gas, etc.). Electrons are drawn across the void from the source or emitter to the drain or collector by an electrostatic field created when a voltage is applied to the gate.